The richest people in the world are frightened

They're keeping more cash in their pockets, a sign of fearfulness. Liquidity, or the proportion of their net worth in cash or cash equivalents, is now at 22.2%, according to a report by the research firm Wealth-X.

That means $2.22 out of every $10 in wealth is held in cash — the highest level since 2010.

The report looked at 2,473 billionaires with a combined wealth of $7.7 trillion.

It's not hard to see why the superrich would want the flexibility that comes with holding large sums in cash. Geopolitical turmoil, terrorism, Brexit, and the US election are adding volatility to global markets amid a grim economic picture.

Here's Wealth-X:

"Billionaires are taking money of the table where available, while uncertainties in the economy and the historical highs found in deals have resulted in cash-flush portfolios."

Other factors are at play here, too. There was an increase in "liquidity events" in 2014 and 2015, with the superrich selling assets and taking their companies public. Here's Wealth-X again:

"Global divestment M&A activity was at a near all-time high and in 2015 IPO proceeds registered a second consecutive year of the strongest performance seen since the end of the global recession. Once equity valuations return to more attractive levels, we expect a movement toward putting liquidity back into deals."

In other words, the superrich have made some money over the past through years by selling assets, and they're holding back from putting that money back in to the market.